I wouldn't count myself as a huge cheerleader for The Exorcist. I don't think it's anywhere near the scariest film ever made, with its clunky screenplay and dated shock effects. However, I would still argue it's an eerie, chilling and superbly acted thriller that William Friedkin directs the hell out of. For Exorcist 2: The Heretic, I just don't know what - yeah, I'm going to say it - I just don't know what possessed anyone from director John Boorman to star Richard Burton to get involved in this messy and unwieldy schlock.

Several years on from the events of the original, and Reagan (Linda Blair) is attending college, whilst also visiting Dr Gene Turkin (Louise Fletcher), a psychologist who specialises in hypnosis, in an effort to discover what happened to Reagan when she was possessed as she remembers nothing of that period of time. Also investigating Reagan is Father Peter Lamont (Richard Burton) a priest who has his own experience of exorcisms and has been tasked to find out exactly what happened, in particular to Father Merrin (Max Von Sydow) whose name has been linked to scandal and controversy since his death at the hands of the demon possessing Reagan. This takes them back into Merrin's history, particularly his time in Ethiopia, when he first encountered the demon that would later take control of Reagan.

When it comes to remakes or sequels, I try to avoid making direct comparisons to the original. I believe each film should stand on its own merits, or fall by its own flaws, and not be unfavourably viewed because of the reputation of its predecessor. Unfortunately, Exorcist 2: The Heretic, fails so much by any standard you can't help but reflect on what a great film the original is.

Its problems start with the screenplay, which doesn't make a lick of sense. For a start, it's established, by the fact that Reagan is at college, that this is some years after the original. Yet it's never explained why it's taken so long for Father Merrin's death to be investigated. As for Father Karras' death...well, he's never mentioned at all. Secondly, I don't think it's ever made clear who exactly the titular 'Heretic' is. Thinking about it, that title could apply to either Reagan or Lamont - hell, potentially even Merrin. Maybe the film did explain it at one point, but I missed it because I was too distracted by the hordes of locusts inexplicably attacking the screen at random intervals.

Yes, locusts. Because Merrin's time in Ethiopia dealing with demons also involved hordes of ravenous locusts, which now make completely unexplained appearances in the contemporary sections of the films. Quite what the significance of the locusts is, is yet another unanswered question. Personally, when it comes to horror films, I don't mind ambiguity or some questions left unanswered - The Shining draws great power precisely from this tactic - but when a film makes a huge point about one particular aspect, like this one does with these locusts, you'd expect something some kind of vague inference as to their significance. But you don't here, and as a result the vast majority of the Africa flashbacks, complete with James Earl Jones as some kind of witch doctor/tribe leader/contemporary doctor (and if anyone can explain THAT to me, I'd greatly appreciate it), are as baffling and incomprehensible as the Iraq prologue was to the first film. This isn't helped by Boorman's intense close-ups of locusts flapping menacingly towards characters that can't help but bring to mind Mothra, from the original Godzilla films.

Another major sticking point, and one that clunks all the more heavily because of the original, is the hypnosis scenes. Here, hypnosis is not just lulling someone into a deep communicable sleep. It's a trance incurred by heavily flashing light bulbs and not just that, but it's also a trance state that someone else can enter if they too are in a trance to see that person's dreams. Rarely, outside the films of Roger Corman and Ed Wood, has a horror film founded itself on such ridiculous science. Yes, many other films may have a similar lack of respect for science, but when you think of the original's spinal tap scene and the creeping fear engendered by the fact that Reagan was baffling modern science, this film's approach to science (not helped by this is a film that takes itself deadly seriously) couldn't seem more wrong. Apparently on its previews, these scenes had the audiences in fits of laughter and you can only sympathise. Richard Burton and Louise Fletcher taking it in turns to balefully glare at Linda Blair while clips of Max Von Sydow are overlaid them would pretty much be the low point off anyone's career.

Fletcher herself is decent enough, but wasted in an underwritten role; while Richard Burton's constant furrowed brow gives Lamont the unfortunate demeanor of a man working off his latest hangover. Linda Blair was always the weak spot in The Exorcist, but you could forgive her for having natural limitations as a child actor. Unfortunately, Exorcist 2: The Heretic proves she's just plain limited. Every word tumbles out of her mouth like a lump of oak and freed from the shackles of playing a possessed girl (any flashbacks to the original demon are played by an extra, unhelpfully not looking a great deal like Blair at all) she's just boring and stiff in the role. Ironically, those come out best are those who chose not to return, such as Ellen Burstyn and Jason Miller.

Sydow gives a little flesh to Merrin's younger bones, but I'll be damned if I can work out why we even need flashbacks to him. What does his past have to do with the present? Who the hell is even possessed by the end? If that's Reagan next to Lamont, who's that on the bed? What the hell is Lamont even doingat this point? The end has bangs and flashes a-plenty, but with little explanation as to what is happening to whom, and why, it's all for very little effect.

Boorman's direction is thus strangled by the unfathomability of the script. Criminally, very little of this is actually scary, eerie or even memorable. The first reappearance/flashback of possessed Reagan gives a little chill, but Boorman overplays it to the point of laughter and there's so little logic to the film that Boorman's directorial outbursts of style seem like the frustrated lashings out of someone so stymied by the material that they'll try anything for effect. Unfortunately this leads to 1930s Ethiopia looking like something out of Star Wars and if there's a funnier intercutting of scenes than the one here of Richard Burton being stoned by a bunch of Africans with Linda Blair falling arse over tits while hoofing it around on stage, I've yet to see it. Presumably the inference is that there's some deep subliminal and psychological connection between Reagan and Lamont. The point or result of that? Who the hell knows.

Part of the beauty of the original was the feeling that Reagan was possessed because the desecration of an innocent little girl was the ultimate insult to God and the sanctity of human life. This tied in with the film's pessimistic view on religion, as seen in the vandalised church and Karras' loss of faith. One genuinely scary aspect was the the central struggle was relatively subtle - the soul of one child was where the demon dwelt, with the inference that this is should be scary because it's so rare for it to happen. That's why no-one really knows how to deal with it.

All this is lost for the sequel. Supernatural possession is seen as easy as catching a cold from someone. Anywhere between four and six people are seen as possessed at various points throughout the film, the shocking effect diluted each and every time. In the original, the demon was crafty and clever; here, it's just cackling and schlocky; a ghost-house ride that can be dealt with with apparent ease. There's no investigation into how these events fit into religious beliefs or scientific beliefs like the first. Science is a hokey futuristic concept and faith...well, for a film with a priest as a main character, there's precious little point to having it, apparently.

That's why, as undeniably fascinating a wreck this is (look, I'd never call it boringas such), it is still a wreck. It's like they took every great thing about the original and decided that was exactly how they WEREN'T going to do it.

By the end one character sobs, "I understand now. The world won't. Not yet". Well, we're still waiting.